1. Field of the Invention
This invention relates a lubricating structure for a gear mechanism such as those for an automotive transmission system.
2. Description of the Prior Art
For example, in an automotive transmission, a gear mechanism having a plurality of coaxial gears are housed in a housing, and the bottom of the housing is used as an oil well and the oil in the oil well is scooped up by the teeth of the gears to lubricate the mating parts. As disclosed, for instance, in Japanese Unexamined Utility Model Publication No. 61(1986)-1771, it has been proposed to level up the bottom of the oil well by providing a baffle plate for each gear or by shaping the bottom of the housing to the shape of the tooth tips.
When the bottom of the oil well is leveled up in such manners, the quantity of oil stirred by the gear can be reduced, whereby stirring resistance is reduced and the gear is lubricated at high efficiency. Further, the oil level can be raised without increasing the quantity of oil and accordingly gear noise can be effectively reduced by the use of viscosity resistance of the oil.
However, in the case of the gear mechanism for the automotive transmission, the oil level inclines according to the running condition of the vehicle. When the bottom of the oil well is leveled up to conform to the shape of tooth tips, the oil in the oil well for a gear can move to the rearward oil well over the baffle portion therebetween, for instance, in response to abrupt acceleration of the vehicle and cannot return to the original oil well soon, which can result in oil shortage to cause seizing in gears and/or increase in gear noise.